"The ability to manipulate our dream worlds goes beyond the science fiction plot of the movie Inception. A dream expert from Harvard University explains how it works.

Some dreams feel so revelatory—if only returning to sleep would take us back there. It turns out, however, that our ability to shape our dreams is better than mere chance. In the blockbuster movie Inception, Dom Cobb (Leonardo DiCaprio) and his compatriots use drugs and psychological profiles to trigger specific dreams in people. Although the heavy sedation and level of detail incited are far-fetched, dream control isn't entirely a Hollywood fantasy.

Techniques to control, or at least influence, our dreams have been shown to work in sleep experiments. We can strategize to dream about a particular subject, solve a problem or end a recurring nightmare. With practice we can also increase our chances of having a lucid dream, the sort of "dream within a dream" that Inception's characters regularly slip into.

The ability to influence other people's sleep worlds is still crude. But emerging technologies raise the prospect that, at the very least, we'll get an idea of what others are dreaming about in real time.

We asked Deirdre Barrett, author of the book The Committee of Sleep: How Artists, Scientists and Athletes Use Dreams for Creative Problem-Solving—and How You Can, Too (Crown, 2001) and assistant clinical professor of psychology at Harvard Medical School, about what dream-control strategies do and don't work—and why.

[An edited transcript of the interview follows.]

We're all familiar with dreams, but what's the scientific definition?
The literal definition is a narrative experience that occurs during sleep. A few people will define it as a REM (rapid eye movement) sleep experience but, actually, the research doesn't support that. Some things that seem to look like dreams occasionally occur in other stages of sleep.

Why do most dreams seem to occur in REM, and what's happening during that sleep phase that seems to produce dreams?
REM is generally the only time during sleep that most of the cortex is pretty much as active as it is when we're awake. During this phase, there are rhythmic bursts of activity in the brain stem. There's one school of thought that this rhythmic firing is the sole cause of dreaming and all the upper cortical activity is a simple response to that. It just doesn't look that way. It looks like the lower brain stem activity wakes the cortex up and then the cortex does a lot of organized, meaningful thinking once it's activated.

The thing that is very frustratingly not neat and clean is that every once in awhile when you wake somebody out of a non-REM period, they report something that looks pretty much like the elaborate narrative of a dream. This is especially common in people who have big traumas and shift workers who have their sleep disrupted, so it may be that it happens mainly when something isn't operating completely properly with the regular sleep cycle.

During dreams, are certain regions more active than others or does that depend on what you're dreaming about?
It's sort of halfway in between the extreme version of either of those.

On average, there are several areas that are more active than they would be during the waking state. Those are parts of the visual cortex, parts of the motor cortex and certain motion-sensing areas deeper in the brain. That's probably related to why dreams are so very visual compared to other sensory modes or types of content and also why they have a lot of motion and action in them relative to our waking experience. The parts of the brain stem that fire those bursts of activity are also active.

There are other areas that are less active on average during REM sleep. Those are the prefrontal areas, which have to do with the fine points of logical reasoning and also where you might say censorship resides. That's not only for censorship of things that are socially inappropriate, what Freud would have meant by censorship of sexual and aggressive impulses, but also the impulses that say, "that's not the logical way to do things." That seems to be why even though we continue to think about all kinds of problems and issues in our sleep, and sometimes come up with really creative, interesting solutions; their logic is less linear than our waking thought is.

Given that there's higher-level thinking going on in our dreams, to what extent can we control them?
That we can control our own dreams is quite true and really much more so than people seem to know or realize. The details of how to do it are very different depending on whether you're trying to induce lucid dreams, whether you're trying to dream about particular content or whether you're trying to dream a solution to a particular personal or objective problem. Another really common application has been influencing nightmares, especially recurring post-traumatic nightmares—either to stop them or turn them into some sort of mastery dream.

So how can you problem-solve in a dream?
Although any kind of problem can make a breakthrough in a dream, the two categories that really crop up a lot are things where the solution benefits from being represented visually, because the dreams are so vivid in their visual-spatial imagery, and when you're stuck because the conventional wisdom is just plain wrong.

You may have heard the example of August Kekulé and the benzene ring, which represents both these themes. He was thinking that in all nonchemical molecules, the atoms were lined up in some kind of straight line with 90-degree side chains coming off it. Once he knew the atoms in benzene, he was trying to come up with arrangements of them that were straight lines with side chains and it just wasn't working. Then he dreamt of the atoms forming as a snake, eventually reaching around with the snake's tail in its mouth. It seems exactly related to the fact that the prefrontal lobes that control censorship are, on average, much less active during dreams.

If you want to problem-solve in a dream, you should first of all think of the problem before bed, and if it lends itself to an image, hold it in your mind and let it be the last thing in your mind before falling asleep. For extra credit assemble something on your bedside table that makes an image of the problem. If it's a personal problem, it might be the person you have the conflict with. If you're an artist, it might be a blank canvas. If you're a scientist, the device you're working on that's half assembled or a mathematical proof you've been writing through versions of.

Equally important, don't jump out of bed when you wake up—almost half of dream content is lost if you get distracted. Lie there, don't do anything else. If you don't recall a dream immediately, see if you feel a particular emotion—the whole dream would come flooding back. [In a weeklong study I did with students that followed this protocol] 50 percent dreamed of the problem and a fourth solved them—so that's a pretty good guideline, that half of people would have some effect from doing this for a week.

What about if you want to, say, dream of a certain person or about a particular experience—how can you do that?
If you're just trying to dream about an issue or you want to dream of a person who's deceased or you haven't seen in a long time, you'd use very similar bedtime incubation suggestions as you would for problem solving: a concise verbal statement of what you want to dream about or a visual image of it to look at. Very often it's a person someone wants to dream of, and just a simple photo is an ideal trigger. If you used to have flying dreams and you haven't had one in a long time and you miss them, find a photo of a human flying.

Image-rehearsal therapy has gotten attention as a strategy to overcome nightmares. How does this technique work, and is it effective?
Different people mean different things by that. The details are different but the techniques are very similar—they all grow out of the observation that when people are having bad, repetitive post-traumatic nightmares, a certain proportion seem to move on to having some kind of mastery dream spontaneously. The same way the nightmares had been re-traumatizing them, the mastery dream seemed to carry over into helping them feel much safer and more healed in their daytime state.

[Therapists or researchers] have the person work out an alternate scenario they want the dream to take, where they might ask them to close their eyes and imagine and generally talk them through a kind of vivid enactment of it. Usually the person incorporates some degree of the rehearsed scenario at bedtime or listens to a tape where the therapist or researcher is recounting the alternate scenario.

Barry Krakow does this in a group format and gets statistically significant, positive outcomes. He gets a remarkably high number of people who don't report the mastery nightmare and yet their nightmares stop and/or their daytime anxiety gets much better. We can't know whether they had a mastery dream and don't recall it or if something else about that positive, soothing imagery as you're falling asleep—even if it does not carry over into the dream—carries over into decreasing the number of the nightmares or the daytime anxiety, heightened startle response and flashbacks. In the one-on-one clinical studies there seems to be a much higher rate of actually having the rather dramatic mastery dream.

In the case of the successful techniques, what may be happening in the brain that allows these dream-control strategies to work?
Only if you're buying this idea that dreams should all be random or are being generated in the lower brain stem is there anything we need to explain about why you'd remember a suggestion you'd made to yourself for dream content or that intensely studying a problem before you fell asleep wouldn't be likely to turn up in your dream. Our ability to request that of ourselves at some point in the future is very analogous to what we might do awake. When it happens in a dream, it's happening in a state that by its nature is more vivid, much more intuitive and an emotional kind of thinking, and much less linear in its logic and much less verbal in orientation. That we're going to respond to this request from this very different biochemical state is what makes it such that sometimes we'll kind of respond but it will be in this vaguely nonsensical kind of way; other times it will be that we have this amazing breakthrough because we're thinking about this problem we've had this false bias about how to solve when we're awake.

Can we dream that we're dreaming?
Yes. That is the most common definition of a lucid dream—a dream where you know you're dreaming as the dream is occurring. A few writers on lucidity have chosen to make some degree of dream control part of the definition, but most choose to see that as a separate, additional element. Lucid dreams are infrequent—less than 1 percent of dreams in most studies—but they certainly do crop up in any large collection of lots of people's dreams.

How can you up your chances of having a lucid dream?
By reminding yourself you want to just as you're falling asleep, either as a verbal statement or idea: "Tonight when I dream, I want to realize I'm dreaming." That's the single most important thing, other than simply getting enough sleep. For any sort of dream recall or influencing of dreams, or for lucidity, simply getting enough sleep is one of the most boring pieces of advice, but one of the most important. When you deprive yourself of sleep, you are getting a lower proportion of REM. We go into REM every 90 minutes through the night, but each REM period gets much longer and occupies a larger chunk of that 90-minute cycle each time. So if you're only sleeping the first part of a normal eight hours of sleep, you're getting very little of the REM sleep you could.

Beyond that, if you check on whether you're actually awake in a systematic way during the day, you'll eventually find yourself doing this in a dream, and that can make it likelier that you will have lucid dreams.

You can do this by identifying something that is consistently or usually different from your sleeping and waking experience. Lots of people find they can't read text in a dream, that if they see text it's almost always garbled or hieroglyphics or doesn't make sense or it's fuzzy. People who can read in a dream will still report that the text is not stable; if they look away and then back, it says something different or there's no longer any writing there. So trying to read something in a dream is a good test for lots of people. Others find that things like light switches and other knobs that are supposed to turn things on and off work normally in their real world and don't do what they expect them to in a dream.

If you work out one specific check and then ask yourself, does everything look logical, you'll find yourself doing that in a dream. Some of these techniques are successful in as many as 10 percent of people in the course of a week for a few studies.

What are less effective ways of controlling a dream?
People who decide that they want to alter their nightmares or solve a problem through lucid dreaming have carved out an infinitely more difficult path—not that it's impossible but there's a lot more hard work and a lot less chance of success that way.

When lucidity was getting press in the 1970s, people were thinking it's a great way to end nightmares and have problem-solving dreams. But it turns out that lucidity takes a lot more effort and happens more unreliably than other forms of dream control. The study where I had students select real-life problems within their ability to solve—with strong motivation, in one week half dreamed about the problem and one fourth dreamed an answer to their problem, and that's much higher than you'd get for lucidity techniques. In transforming-nightmare studies, that rate is higher and happens quicker than it does for lucidity. So approaching these goals by almost demanding that the dream do what really you can do much better awake is not the smartest approach.

What about controlling someone else's dream—is this possible?
Occasionally there are some ways that one might influence someone else's dream content ahead of time via waking suggestions or during sleep via sensory stimuli that are impinging on the dreams.

The auditory seem to things work best, such as water or a voice saying something. Very strong stimuli wake us up. You want it to get in some narrow threshold where it gets detected by the brain and processed but it doesn't wake you up, and then there's a shot at it getting incorporated into the dream.

In his research on lucid dreams, psychophysiologist Steve LaBerge tested a dream light that sleep subjects wore on their faces that detected REM and flashed a low-level, red light during that phase. He found that it often got incorporated into people's dreams—they saw a pulsing red glow. If you combine that with the suggestion that when you see the flashing red light you know you're dreaming, you can promote lucidity.

Magnetic input is being done in the waking state to improve depression and to halt psychomotor seizures. If you can influence mood awake, it would seem you could influence the mood of a dream. We will get more precise about what we know about different brain areas and targeting magnetic signals toward them.

Lastly, we can image the brain well enough awake or asleep to know things like: there's an unusual amount of motor activity; or this person is probably doing mathematical calculations right now; or this person is processing incoming language or speaking or writing or is very likely sad or very likely happy. And we will probably get better at that. We can already do more things with animals: If you've trained rats in a maze, during REM sleep they look like they're dreaming the maze—they show the same pattern of firing left-right turns. That's done by sinking needle electrodes into their brains, which we obviously don't do to humans. But we may get good enough at imaging nonintrusively from the outside to see a lot more about the content. That's not directly controlling a dream, but it's one of the things that you might want to know if you were trying to control dream content.
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